The control of a thyristor-type or triac-type power switch requires extracting or injecting a current from or into the gate thereof. The generation of this current may involve using a specific circuit to generate a current galvanically isolated from upstream circuits, which operate under a different voltage or with a different potential reference. This is particularly true in power applications where the switch controls an AC load or is connected to terminals of an AC voltage, as is the case for a rectifying bridge.
Other applications avoid an insulation transformer at the cost of utilizing a pulse control of the thyristors. For example, U.S. Pat. No. 9,525,361 (incorporated by reference) describes a rectifying bridge having two anode-gate thyristors provided in the lower portion of the bridge, that is, with the anodes connected to the most negative potential of the rectified voltage (typically, a reference potential or ground).